Nice and simple script that does what I and properly many many others always wises YouTube would have implemented for many years. A simple size and quality selector. Works great and very easy too configure. Who would have thought that something such simple in concept would require soo much code.
The documentation for this script is also very thoroughly.
http://eugenox.appspot.com/script/yays

This script is simply awesome. The on/off function is very cool. Thanks you very much.

Works fine in Chrome, great work ;)

It blows me away that YouTube hasn't implemented this feature themselves, so I've go to thank the author of Yays! for making this functionality available. I picked it up for the ability to disable AutoPlay, but the fact that it also lets you auto-set the quality of all videos to max is amazing!

My only gripe is that it doesn't work when my other favorite script, YouTube Enhancer, is installed. But autoplay and auto-max quality are better features than what I use TYE for, so I don't mind disabling it until I need one of it's features.

This userscript is probably the best I've ever seen. It functions beautifully:
I like to watch videos in high quality, but 1080p is unnecessarily high and it takes too long to load, so I can simply use this script and set it to 720p. It will now automatically set my videos to 720p OR the next highest resolution available (there is a big difference between 360 and 480).
Additionally, I can choose to set the video width to "fit" which perfectly matches my browser window.
Finally, the function I love the most is the autoplay which allows me to open YouTube videos in background tabs without them playing UNTIL the tab gets focus. With this, I can open several videos from a user and let them load in the background.
The script settings are integrated seamlessly into the YouTube page and it is ALWAYS kept up to date.

I created my userscripts account just to rate this script :). tested on FF 3.6.4. works flawless. great stuff!

Everything works perfectly on Chrome, the Auto autoplay feature works fine too.

Exactly what I was looking for! I report flawless (so far) compatibility with Safari 4.0.5 with GreaseKit on Mac OS 10.6.3.

I've been looking for something like this for a while. I'm using several youtube scripts simultaneously and the hd and autobuffer feature got broken somewhere in between. But Yays! works! :)

Just a great and verry useful script
Thanks for the great updates!

I like the new options button below the video
Now i've got more space for download script buttons ;)

This script is simple, compete and well-integrated. No fuss, no delay, no complex settings panel. Kudos to the writer!